It is an absolute fact of spiritual life that Lord Krishna existed within us as our soul atman. Prime reason why to reach Lord Krishna within, one has to take inner journey that too guided by sermon of Bhagavad Gita.
Allegorically Krishna is soul atman existing within our heart. Arjuna a spiritual traveler by birth did not want to indulge in war with his cousins, close relatives and friends. Being spiritual he feigned cowardice. It was then he automatically reached state of enlightenment. And during those moments of his dialogues with Lord Krishna he realized that the human form was only a garb for soul atman within and the actual master and controller of human body was soul atman.
The moment Arjuna realized shallowness of his thinking process; death carried no meaning for him any further. This resulted in Arjuna picking arms and prepared himself to fight head-on. Dialogues of Arjuna with Lord Krishna gave clear direction to Arjuna that soul atman was indestructible, could neither be created or destroyed. In fighting his arch enemies Kauravas he would not be killing anybody.
Arjuna also realized that his personal self did not matter in battle of Mahabharata. It was a fight to re-establish Dharma (righteousness) against evil forces of adharma (lawlessness). If his close friends and relatives chose siding adharma then it was their problem. Arjuna had to fight for the sake of his countrymen and soldiers as he was the chieftain of all.
By giving a patient hearing to Lord Krishna within, Arjuna finally won the battle of Mahabharata, battle of Dharma (righteousness).
Allegorically the dialogues between Arjuna and Krishna convey one meaning! Every single moment of life thousands of thoughts passed through our brain both negative and positive. By taking guidance from Lord Krishna within we can demolish all negative forces of nature within. In this churning of thoughts called Samudra Manthan in Hinduism both Amrita (elixir of life) and Vish (poison) is produced. Seekers used Amrita to awaken their kundalini shakti fully and the Vish is normally retained in the neck or body, prime reason why body of Krishna or Shiva is shown blue.
The battle of Dharma, battle of Mahabharata is all about Samudra Manthan going on within our own body. Indulging in spirituality detailed in Bhagavad Gita we can realize what spirituality truly was all about and finally make efforts to crossover ocean of Samsara (worldly life) to reach state of enlightenment, also called self realization.